Such a device is disclosed in German Patent specification No. 3233 940. With this known quick-acting clamping device, high clamping forces and at the same time a large axial clearance movement of the clamping anchor can be achieved, so that comparatively large idle strokes of the anchor can be achieved within a very rapid clamping and release cycle. A pressure plate on the sliding member of the toggle lever system is, for this purpose, formed as a piston and has a fluid pressure connection at its piston-side boundary surface with the pressure chamber of the clamping piston and is fluid sealed against the housing. There is thus a functional division between an initial idle stroke and a subsequent controlled clamping and locking of the clamping anchor. The clamping or pulling anchor, which is mounted upright in the housing, has a rhombus-shaped T-groove block at its free end which permanently projects to a greater or lesser extent into the clamping zone and engages, for example into T-grooves or into carriage aprons of the article to be clamped. The clamping anchor which is raised sufficiently high before clamping by means of a sliding piston, is, after it has moved into its locking position, at first so adjusted by means of a rotary mechanism consisting of two oppositely acting, piston-driven toothed racks which act in the rotational direction upon a toothed ring which is slidable axially along the clamping anchor, that the T-groove block cannot escape from its seating when the pulling anchor is pulled up, i.e. at clamping. Clamping is effected by means of the toggle lever system when the levers adopt extended positions.
The main object of the present invention is to improve a clamping device as initially described in such a way as to create a compact, robust device of small dimensions, which makes possible reliable and economical clamping, and which preferably does not have any clamping elements which, in use, extend into and obstruct the clamping region of a table or stand so that, for example, a tool changing carriage can be brought unimpededly right up to the edge of the table for the purpose of loading it.